Objectives To investigate the association between increased adiposity, increased circulating insulin levels and ovarian dysfuntion in pre-natally androgenized female rhesus monkeys, as part of a study investigating the etiology of polycystic ovarian syndrome (PCOS). ABSTRACT:Twenty-five female rhesus monkeys, androgenized prenatally, exhibited an increased incidence of anovulation, enlarged polyfollicular ovaries, hyperandrogenism and hypersecretion of immuno- and bio-active luteinizng hormone, compared to 28 age- and size-matched control females. Reduced ovulatory frequency (oligoovulation) in prenatally androgenizsed females was associated with increased adiposity and elevated fasting serum levels of insulin. Conversely, adiposity and fasting serum insulin levels were not different between oligoovulatory and ovulatory control females. Overall measurements of adiposity and fasting serum insulin levels were similar in both prenatally androgenized and control female groups. However, (i) skinfold thickness measurements of upper and middle regions of the abdomen were significantly greater in prenatally androgenized females than in control females, and (ii) a siginificant positive relationship between body mass index (BMI) and fasting sreum insulin levels was found in prenatally androgenized females, but was not present in control females. Therefore, adult female rhesus monkeys, prenatally exposed to androgen, may exhibit ovarian and physiological changes similar to PCOS in women. Key words infertility, anovulation, adiposity, polycystic ovarian syndrome, insulin.